Top gun type nylon strap for my mark XVIII please help

I am looking to get the IW327002 mark XVIII, but really want a strap like on the BP top gun. Any suggestions as where I might be able to find one?(BP strap is to big to swap out with the mark of course). Any help anyone can provide would be of great assistance.

The Pilot’s Watch Mark XVIII TOP GUN Miramar is based on the traditional observer’s watch